Pontoon



April 1953 R. B. STEIDLEY 3,083,665

PONTOON Filed 001;. 51, 1961 FIG 3 ROY B. STEIDLEY INVENTOR.

AGENT t e. s s as use a a ,e ics ra-s ame firs 9 9 a ti e' r t fillinas? is elififigi Fatented Apr. 2. was

skin bonded on the expanded cellular polystyrene, the 3,983,655 skinwould add little if any strength since, upon being EG-NTGGN 2 t'llainis.ill. I114 --.5)

,nor, by means g (3a., Terminal T his invention relates to flotationequipment, and more specifically to a pontoon. Among their many uses,pontoons are employed for the support of piers, wha-rves, work andequipment platforms, gasoline and oil dispensing facilities, etc.

Although their origins are lost in antiquity, previously employedpontoons have been less than satisfactory in certa n regards, and theirimprovement has remained a desirability. Since the load-carrying abilityof a pontoon is equal to the weight of the amount of water it displacesless its own weight, it is very desirable to keep the weight as low aspossbile in a pontoon of given volume. The cost of each pontoon is, ofcourse, an important considera tion and this becomes especiallysignificant where, as is frequently the case, ontoons are used in largenumbers. Low weignt, however, is no advantage where it is obtained bythe sacrifice of strength. The use of lessened amounts ofi materials ormaterials which are light but of little strength results in a pontoonwhich has not the structural strength or integrity requisite to itsbearing a full load imposed by the structure it supports and by thewater. Similarly, low initial cost is of no avail where it is obtainedat the sacrifice of durability. Until the present, unfortunately,strength and durability have strongly tended to be accompanied byexcessive weight and/or high cost.

Many pontoons previously have been made of wood, which is initiallyheavy and quickly becomes heavier through becoming waterlogged. Problemsexist in the sealing of the joints in a wooden pontoon, and the wood issoon deteriorated and consumed by marine organisms and fungi. Woodenpontoons with waterproof skins have been proposed. Although animprovement, these still are subject to puncture by blows from boats,etc., and thus retain the same disadvantages as a plain wooden pontoononce water is admitted to their interiors.

Other pontoons have been made of steel, which is excessively weighty andsubject to chemical attack by the salt waterj and still others have beenmade of concrete. (3f attractively low initial cost, concrete pontoonsare too easily cracked in transit or in service. Like a steel pontoon,they sink and are of no further usefulness once water has entered andfilled then In an effort to achieve light weight combined with strengthand relatively low cost, pontoons have been made ofi blocks of expanded,cellular, polystyrene materials. These have had the disadvantage of aninherent friability which causes them to spall and be rubbed away wherein contact with a shifting pier, etc. Polystyrene pontoons, like othermaterials, become encrusted with bmnacles, and in many cases it isrequired that these be periodically removed. Because of its crumblynature, a polystyrene pontoon is damaged by the removal 05 barnacles,for chunks of the pontoon material are pulled away in scraping andchipping oil the barnacles. ttempts have been made to cover expandedpolystyrene pontoons with protective: skins. for the polystyrene doesnot bond efiectively with relatively inexpensive, rigid skin materials.The skin, where bonded to the buoyant block of polystyrene, ordinarilyis flexible and stretchable, for polystyrene will bond with rubber andthe like. Even if more expensive materials were employed, as would benecessary in providing a rigid Such skins have ordinarily been loose,

stressed by forces imparted to it through the polystyrene, it wouldmerely shear or pull away the material to which it was bonded at theexterior surface of the polystyrene block.

in common with steel, a polystyrene pontoon is vulner able to theetlects of acids and corrosives which may be spilled on it through, fiorexample, the planks of a pier, and in addition is subject to attack bymany organic solvents, etc.

it is a major object of the present invention to produce a pontoon ofmaximum efiiciency and durability, and this at minimum cost.

A related object is to provide a pontoon of given displacement which isof lighter weight but of fully adequate strength.

Another object is to provide a pontoon of superior esistance to thedeteriorating effects of salt Water and which is not subject todeterioration or sinking upon being punctured and filled with saltwater.

A further object is to provide a pontoon having a rigid skin and whichremains virtually waterproof even upon puncture of the skin.

Yet another object is to provide a pontoon the exterior and interior ofwhich are substantially immune to the etiects of acids, bases, salts,and solvents.

A still further object is to provide a pontoon construction which, whileemploying a more desirable and concurrently more expensive material,nonetheless is of superior economy.

Still another object is to provide a method of fabricating a plasticpontoon.

Additional objects and advantages will be apparent firom specificationand claims and from the accompanying drawing illustrative of theinvention.

in the drawing:

FIGURE 1 is a side view, in vertical section, of a pontoon constructedaccording to the invention and bearing a member or members of a pier orthe like;

HGURE 2 is an enlarged sectional view of a portion of the glass fiberreinforcements oi the lid preparatory to introduction of the resin;

FIGURE 3 is a view similar to FEGURE l and showing an embodiment of theinvention wherein the pontoon is more elongated and has employed thereina cross-wall; and

FIGURE 4 is an enlarged sectional view of the pontoon lid and side wallconstruction.

With reference now to FIGURE 1, the pontoon 10 floats in water andsupports heavily loaded planks of a pier or other supported body .11.Although shown in vertical section, the pontoon 19 will be understood tobe shown in the form of a rectangular parallelepiped with square bottomand of which one wall is omitted in the sectional view presented. Otherforms including cylindrical, spherical, or any other desired shape arereadily possible in construction of the pontoon 19 according to theinvention. The form of a rectangular parallelepiped is preferred,however, for the greater stability ofi such a body in the water and forthe linear relationship between the depth of partial submersion of thepontoon and its buoyant force.

The pontoon 153 is held in place by the downward force of the supportedbody ill and, where desired, by cleats 12 attached under the supportedbody 11 in framing relation to the top of the pontoon ill.

The pontoon it comprises a skin 13 made of a glass fiber reinforcedresin. Because of the properties of other components, as more fullyexplained later, a polyester resin is employed, and this is of greatadvantage because J; ofits' relative cheapness combined with itsrigidity, toughness, imperviousness to water, and durability whencombined with the glass fibers. Where it is desired to increase theresistance of the pontoon to fire, approximately (by weight) of antimonyoxide mixed with chlorinated paraifnl is added to the resin. The skin 13has a bottom 14, three sides .15, 16, 17, and a fourth side (omit-fedfrom the view in vertical section) which together with the bottom 14 andsides 15, 16, 17 forms a hollow body. Each side wall has an upper edgesuch as 18, and all these edges are trimmed to lie in one plane. Theskin 13 is substantially unstret chable and for lightness and economy ismade as thin as conveniently possible. A thickness of;% inch is adequatefor strength and is conveniently produced while using known technics; athickness of over inch is undesirable in pontoons of ordinary siz'esince it is unnecessary for strength, increases weight, and adds tocost. For reasons which will become evident, the; side walls of thepontoon (see the walls 15, 16 prefei ably taper inwardly from theirupper edges 18 to the bottom 14. A taper of two degrees is generallysufficient, and to this extent the pontoon deviates from therefctangularparallelepiped form.

A layer of polyurethane foamed material 19 covers and is bonded to theinner surface of the skin 13 throughout the bottom and sides of thehollow body formed by the skin. The foam itself thus forms a hollow body19 lining the skin and having a bottom and side walls such as 21 whoseupper edges were flush with the upper edges 18 of the corresponding sidewalls of the skin. The preferred foam may currently be purchased underthe designation of Hitco 1.5R, 1.5 lb./ft. density, polyurethane plasticfoam components, marketed by the H. I. Thompson Fiber Glass Company ofLos Angeles, California. This product has been found superior because ofits negligible shrinkage when poured, a factor of importance inobtaining a good bond between the foam and skin and in preventinginwardzdenting of the skin and other deformations which would accompanyshrinkage. The foam is of closedcell structure, tough, rigid, notsubject to crumbling or spelling under forces in shear or tensionbetween itself and the skin; and firmly bonds itself to any surface whenit expands and cures.

It is of importance that the entire skin 13 is not filled with thefoanr19. v The foamedmaterial is of considerable cost per cubic foot andcurrently is considerably more expensive than expanded, cellular,polystyrene materials. Byleaving a large void in the pontoon interior,however, and 'using only the material actually required for ade quatestrength, the cost is sharply reduced and is highly preferable to, forexample, that of a solid block of expanded polystyrene. In arepresentative application, a pontoon of exterior dimensions of 48 x 48x21 inches in height employs a foamed, hollow body whose bottom is 5inches 'in thickness and whose sides are four inches thick; and this hasbeen found completely adequate for supplying all needed strength. It isof importance that 4 supported body :11 and the upper edges of thesidewalls of the skin 13 and foam 19, and its outer surface lies inbearing relation to the supported body 11. The upper edges of thesidewalls of the foam 19, meanwhile, are in bearing relation to the lid23 and hence, through the latter, to the supported body 11.

The lid 23 is of rigid construction to prevent its being dented ordished and must be of sufiicient strength to withstand torsional loads,imposed upon it by shifting rotations of the supported body 11, whichtend to twist the pontoon 10 about its horizontal axis. The second skinor lid 23 is made of glass fiber reinforced resin and is of the order oftwice the thickness of the first skin 13.

As shown in FIGURE 2, the lid 23 is reinforced by a layer of glass fibercloth 26 placed next to the lid inner surface 24 and a glass fibermat'27 adjacent the smooth outer surface 25. A mat which is to inchthick is preferred' and contains numerous glass fibers of uniformlength, unwoven but randomly distributed to form a uniformly thick,highly porous sheeting :of fibers held in compacted condition by aresinous binder the same as or compatible with the construction resin.The latter, as in I the skin, is a polyester. A representative weightfor the glass fiber mat 27 is 1 /2 -oz./ft.

the exterior surfaces of the sidewalls such as 21 and bottom 20 oftheifoamed, hollow body '19 are securely bonded to the,overlying;skin13. The inner surfaces of the side walls 21 of the foamed body, also ofits bottom 20 is desired, are covered by and bonded to a thin, light,substantially non-stretchable material 22 of good strength undertension, Paper, which is relatively excellent in tensile strength, hasbeen utilized for this purpose with good results;

The foamed, hollow body 19, exteriorly covered by the skin 13, is openat'its top; and this opening is covered and the hollow body closed bythe lid 23, whose inner surface overlies and is sealingly bonded to theflush upper edges 30, 18 of the sidewalls of the foam 19 and skin 13.The lid 23 thus is at once a diaphragm for watertight closure of andformingthe top of the hollow body .19 and a second skin which is appliedto the upper edges of the sidewalls ofth'e foam. The lid is disposedbetween the The glass cloth 26 is placed next to the inner surface ofthe lid 23 because it very greatly increases the resistance of the lidto forces imposed on the outer face 25 and tending to dish the lidinwardly. Since such forces are not imposed on the lid inner face 24, noglass cloth is required at the lid outer face 25.

In a modification shown in FIGURE 3, the pontoon 10A is elongated tosuch an extent that adequate rigidity of the lid 23A cannot be obtainedwithout excessive thickening of thelid and consequent increases inweight. To avoid this undesirability, the lid 23A remains the samethickness as before, and a cross-wall 28 made of the polyurethane foamedmaterial is provided which extends across the hollow interior of thepontoon 10A. The cross-wall 28 is integral with the hollow body 19Aformed by the foam, is footed on the hollow body bottom 14A, and has anupper edge 29 flush with the side wall upper edges 30A. The cross-wallupper'edge 29 thus bears against and supports the middle of the lid 23A,to which it is bonded. The crosswall 28 has oppositely disposed faceswhich are covered with the paper or-the like thin, substantiallynon-stretchable sheet material 22A.

7 The means bonding the lid or second to the foamed material is the sameas employed in the embodiment shown in FIGURE 1 and preferably is thesame resin employed in construction of the first skin 13A and lid 23A.Powdered asbestos is added to the resin to form a thick paste. Care isemployed to apply the resin paste in such manner and location as to sealthe pontoon 10 for rendering it watertight.

The method of fabricating the pontoon 10 comprises providing a femalemold of the desired outer dimensions of the pontoon. To provide forlater release of the skin 13 from the mold, a water-soluble mold releasecompound, such. as polyvinyl alcohol, is spread over the mold innersurface. The skin 13 then is laid up by applying and rolling out, on themold bottom and sidewalls, randomly oriented chopped glass fibers andthe polyester resin. The skin 13 is curedbefore applying the foamedpolyurethane, fcr application of the latter to the uncured skin resultsinshrinkage of the foam away from the skin and ing the sidewalls of theskin. More of the polyurethane foam components then are poured into theskin in the space between the skin and second mold walls. The amountemployed is that which produces sufficient foam to cover the skin to theupper edges of the skin sidewalls.

Preparatory to insertion of the second mold and pouring the sidewallfoaming material, however, the faces of the walls of the second mold arecovered with paper or the like thin, strong sheet material, which isdetachably attached to the mold. After pouring, the foam is allowed torise and cure, whereupon the paper is detached from the second mold,which is removed. As it is firmly bonded to the foam, the paper remainsin place; besides adding strength, it provides for easy removal of thesecond mold.

The foam-containing skin 13 then is removed from the female mold, thisbeing facilitated 'by introducing compressed air between the skin andfemale mold to break loose the mold release compound. Any of the latteradhering to the mold and skin is washed away with water. The second moldis removed at a time prior to installing the lid.

Excess foam then is trimmed from the hollow body sidewalls 21 to maketheir upper edges flush with the skin upper edges 18.

The lid 23 next is made in form of a glass fiber reinforced resin plateof a size suitable for forming a Waterproof lid for the pontoon. It isdesirable that the edges of the lid 23 lie flush with the outer faces:of the corresponding sidewalls of the skin 13. In fabricating the lid23, the glass fiber mat is placed on a smooth work surface which iswaxed or otherwise provided with a parting agent. The glass cloth 26then is laid over the glass fiber mat 27 and the polyester resin isworked into them. After curing, the lid 23 is trimmed to size, thenbonded in place on the pontoon 1G with a polyester resin paste. Caremust be taken to provide a good coverage of the top edges 3%) of thefoamed material walls, including the cross-wall 28 (where this isemployed) to provide the largest possible bonding area between the lidand foamed material. FIG- URE 4 shows the bonding means 31 between theupper edge of the hollow body side wall 21 and the lid 23. The bondingmeans 31 also preferably extends between the upper edge 18 of the skin.16 and the lid 23. The illustrated employment of the bonding means 31is typical at all points of contact of the lid 23 with the hollow,foamed body 19 both in the embodiment of the invention shown in FIGURE 1and in the embodiment shown in FIG- URE 3.

The above-delineated method will be found superior in results to amethod wherein the polyurethane foamed resin components are sprayed inplace in the skin to form the foamed body sidewalls and bottom. Sprayingresults in loss of material and an undesirable increase of density ofthe resulting foam. Shrinkage also is severe, and the sprayed foarnshrinks to its air-exposed side, thus pulling with it and deforming theouter skin. Moreover, it is difficult if not impossible to obtain auniform wall thickness when the foam is sprayed. In ensuring that allareas are of the required minimum thickness, other areas inevitablybuild up to several times the desired thickness. This wasteage of therelatively expensive foam defeats a primary purpose of the invention,that of best economy linked with efiiciency and durability.

The present method also excels over spraying or pouring the foam to castit in the female mold, with subsequent laying up of the skin over thefoam. This method is unsatisfactory because of the virtual impossibilityof freeing the cured foam from the female mold without damage to thefoam outer surface.

The saving of foamed material 19 by virtue of the pontoon interior voidresults in a great saving in cost. Meanwhile, the foam 19 is of suchthickness as to be able to bear all the load imposable on the pontoon bydisplacement of water equal to the pontoons submerged volume. To makethe pontoon even stronger would be 6 to add strength not needed;therefore, the interior void from which the superior economy of thepontoon stems in no wise subtracts from useable strength.

Because the chief load-bearing element is the foam 1%, it is possible tomake the skin 13 of quite thin construction, again saving in both weightand cost. The skin 13 of course keeps the foam 19 dry and protects itfrom abrasion and puncture; but very importantly, it adds a stressableouter layer which greatly adds to the strength of the foam. Strengthsimilarly is aded by the thin sheeting 22 covering the interior faces ofthe foamed walls. The glass fiber resin skin 13 and top 23 are immune tosalt water and substantially all other materials which might be broughtinto contact with the pontoon, as by spillage through the planks of apier 11 supported by the pontoon 10.

Even upon puncture of the pontoon skin 13, as by being rammed by a boat,water still cannot enter the interior void of the pontoon 10 so long asthe foam 19 is not pierced throughout its thickness. The polyurethanefoam .19 is of closed-cell construction, and water will not percolatethrough it; its absorbency of water, for practical purposes, is zero.Upon puncture of the skin 13, there fore, the foam 19 itself preventsthe entry of water into the interior void. The foam .19 also isresistant to practically all chemicals in concentrations rapt ever to beencountered in service.

Actual puncture of both the skin 13 and foam 19 so as to allow up tocomplete filling of the inner void does not result in sinking of thepontoon 10 or loss of all useful buoyancy. The foam 15? itself suppliesmuch buoyancy and not only maintains the pontoon 1t) afloat but keeps itin useful service.

Employing the lid 23 in a manner wherein it is merely squeezed betweenthe foam l9 and the flat bottom of the object 11 supported requires onlythat the lid have compressive strength; thus, from this standpoint, itmay be made as thin as may be desired. Torsional forces imposed IOII thepontoon 10 through the lid 23 require, however, that the lid thicknessbe increased over that of the thin skin, but even upon this increase thelid still is light in weight and favorable to frugality in the use ofmaterials. Because of savings in this regard, but particularly inconsequence of the savings in the amount of the foamed material '19employed, the pontoon 10 can be more cheaply constructed than previousplastic pontoons in spite of the fact that it employs a more expensivefoamed material.

While only one embodiment of the invention, together with modificationsthereof, has been described in detail herein and shown in theaccompanying drawing, it will be apparent that various furthermodifications are possible without departing from the scope of theinvention.

I claim:

1. In combination with a supported body, a pontoon which is floated inwater and which contributes to support of the body, said pontooncomprising:

polyurethane foamed material forming a hollow body having a bottom wall,side and end walls with upper edges, and an open top; glass fiberreinforced resin lid underlying the supported body and receiving thrustand torsional loads from the latter, the lid being of a given thicknessand rigid under the torsional loads imposed by the supported body andlying in load-bearing relation between the latter and the upper edges ofthe hollow body side and end walls, the open top of the hollow bodybeing closed by the lid; an adhesive bonding the lid on the upper edgesof the hollow body side walls; and a glass fiber reinforced resin skinof the order of half the given thickness of the lid and bonded to andcovering the hollow body exterior, the skin lying between the hollowbody and the water in which the pontoon floats. I 2. The combinationclaimed in claim 1, the hollow 7 bqdy further having a polyurptllanefoam cross-Wall integr'l therewith,- the; cross-wan bifig fcioted 611the E0? fofii wall and bqrldedto the Iefigtlziwis middle of the lid, towhich the cross-wall is in supporting flation.

Refrencs Cited in the file of this patefit UNITED STATES PATENTS CrosbyD60. 28, 1945 Wiley "2 1 116 5, 1945 1 Sampson Fb. 13, 1951 0

1. IN COMBINATION WITH A SUPPORTED BODY, A PONTOON WHCICH IS FLOATED INWATER AND WHICH CONTRIBUTES TO SUPPORT OF THE BODY, SAID PONTOONCOMPRISING: POLYURETHANE FOAMED MATERIAL FORMING A HOLLOW BODY HAVING ABOTTOM WALL, SIDE AND END WALLS WITH UPPER EDGES, AND AN OPEN TOP; AGLASS FIBER REINFORCED RESIN LID UNDERLYING THE SUPPORTED BODY ANDRECEIVING THRUST AND TORSIONAL LOADS FROM THE LATTER, THE LID BEING OF AGIVEN THICKNESS AND RIGID UNDER THE TORSIONAL LOADS IMPOSED BY THESUPPORTED BODY AND LYING IN LOAD-BEARING RELATION BETWEEN THE LATTER ANDTHE UPPER EDGES OF THE HOLLOW BODY SAID AND END WALLS, AND OPEN TOP OFTHE HOLLOW BODY BEING CLOSED BY LID; AN ADHESIVE BONDING THE LID ON THEUPPER EDGES OF THE HOLLOW BODY SIDE WALLS; AND A GLASS FIBER REINFORCEDRESIN SKIN OF THE ORDER OF HALF THE GIVEN THICKNESS OF THE LID ANDBONDED TO AND COVERING THE HOLLOW BODY EXTERIOR, THE SKIN LYING BETWEENTHE HOLLOW BODY OF THE WATER IN WHICH THE PONTOON FLOATS.